Field of the Invention
The present invention relates generally to safe propulsion systems for use with a missile or like aerial projectile, and more particularly to an improved safe propulsion system which is suitable for use to operate the divert thrusters and the attitude control thrusters of such a missile while using non-toxic propellants which are entirely non-reactive during storage, transportation, and handling.
The field of missile science has advanced rapidly during the latter half of the twentieth century from its relatively primitive beginnings. Early guided missiles were essentially experimental, pilotless aircraft which were operated by radio control systems. The tremendous technological advances in electronics have been accompanied by similar advances in other essential fields such as rocket propulsion, inertial guidance and control systems, aerodynamics, material sciences, and radar systems. As a result, guided missiles today are mass-manufactured for a variety of purposes, ranging from military applications to carrying scientific instruments for use in gathering information at high altitudes, either within or above the earth's atmosphere.
While such guided missiles may vary considerably both in application as well as size, they all include three essential components: a power source for propelling them, a mission payload which is to be carried by the missile, and a guidance and control system. The first of these components is the power source, which may be either a self-contained rocket engine, or an air-breathing jet engine, depending on the application of the missile and intended altitude at which the missile is intended to fly. The second of the aforementioned components is the mission payload, which, as mentioned above, may vary widely, varying from scientific instruments, to surveillance equipment, to explosive warheads.
It is the third of the three essential components of a missile, namely the guidance and control system, which is the focus of the present invention. The internal guidance and control system of a missile includes two elements, the first being the "brains" of the guidance and control system, or the inertial navigation system of the missile. The second element of the guidance and control system is the apparatus which is used to produce the force necessary to guide the missile in its course. While in small missiles this force may be produced by moveable fins and other similar airfoils, in many missiles this apparatus typically includes the divert thrusters and the attitude control thrusters.
The divert thrusters are capable of producing a substantial amount of thrust which is used to effect substantial course changes, generally in two axes which are each orthogonal to the main longitudinal axis of the missile. The attitude control system thrusters, on the other hand, are used to effect a much finer degree of control on the missile, rolling it around its main longitudinal axis in either direction, or making fine course changes in one or more directions orthogonal to the main longitudinal axis of the missile. The divert thrusters and the attitude control thrusters are thereby used to effect control on the course of the missile, as directed by the inertial navigation system of the missile.
Three different types of propulsion systems have been predominantly utilized in the past for divert and attitude control systems used in missiles. These three propulsion systems are liquid bipropellant systems, liquid or gaseous monopropellant systems, and solid propellant systems. Although these three types of systems are all presently utilized, each of them has substantial disadvantages which are inherent in their use, as will become evident in the discussion to follow.
The first of the three systems widely utilized is the bipropellant system, which uses a distinct fuel and a distinct oxidizer. Typically, such liquid bipropellant systems use hydrazine or monomethylhydrazine as the fuel, and nitrogen tetraoxide as the oxidizer. In some applications, bipropellant systems use gels instead of liquids.
Such bipropellant systems present an extreme disadvantage in that they are highly toxic, and, as such, are completely unsatisfactory for applications requiring non-toxicity. In addition, the bipropellant systems are subject to detonation and rapid combustion when dropped or exposed to a fire, making them at least potentially highly dangerous. Finally, bipropellant systems are also dangerous in military field applications, where a stray bullet can potentially destroy the missile and everything in close proximity to it.
Liquid or gaseous monopropellant systems typically also use hydrazine as a monopropellant fuel. Such monopropellant hydrazine is also highly toxic, and once again hydrazine is unsatisfactory for use in applications which require non-toxicity. Monopropellant hydrazine systems are also subject to detonation and rapid combustion when dropped or exposed to a fire, or when hit by a stray bullet. Hydrazine monopropellants are also subject to detonation when heated to approximately 550.degree. F. As such, monopropellant systems present many of the same disadvantages as bipropellant systems.
The third type of propulsion system is the solid propellant system, which presents an advantage over the aforementioned liquid bipropellant and monopropellant systems in that solid propellant systems are relatively non-toxic. Solid propellant systems will, however, detonate when exposed to a fire or hit by a stray bullet. In addition, solid propellant systems present several significant disadvantages not found in liquid bipropellant and monopropellant systems.
First, solid propellant systems are not capable of efficient on-off pulsing operation, which presents a heavy disadvantage when solid propellant systems are used in divert and attitude control propulsion systems. In addition, solid propulsion systems have other significant operational disadvantages, such as relatively heavy weight and a poor ability to allow control of the system center-of-gravity. As such, solid propulsion systems are even more disadvantageous in operation than are the aforementioned liquid bipropellant and monopropellant systems.
It is accordingly the primary objective of the present invention that it present an improved propulsion system useable for divert and attitude control systems, and a related method for use thereof, which system and method use non-toxic propellants exclusively. As such, it is a further objective of the present invention that both the fuel and the oxidizer be non-toxic to thereby eliminate one of the most serious drawbacks of previously known liquid or gel bipropellants or monopropellants. It is an additional objective of the propulsion system and the related method of the present invention that the propellants not be subject to detonation in a fire, when hit by a stray bullet, or when subjected to high temperature.
It is a further objective of the propulsion system and the related method of the present invention that the propulsion system be efficiently operable in an on-off pulsatile manner. It is yet another objective of the present invention that the improved propulsion system present excellent center-of-gravity control such that the characteristics of the missile in which the propulsion system is installed will feature excellent dynamic center-of-gravity characteristics. It is still another objective of the present invention that the weight of the improved propulsion system be relatively light in comparison to solid propulsion systems, and comparable to or less than the weight of previously known liquid bipropellant or monopropellant systems.
The propulsion system of the present invention must also be of a construction which is both durable during operation, and long lasting in a storage situation, and it should further require little or no maintenance to be provided throughout the time that it is stored. In order to compete effectively with previously known liquid bipropellant and monopropellant propulsion systems, and with solid propellant propulsion systems, the propulsion system of the present invention should be of comparable cost to these previously known systems, or less, to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the propellant system and the related method of use of the present invention be achieved without incurring any substantial relative disadvantage.